How to expand a Scrollbar in Tkinter when working with a pre-made user interface (pygubu)

PyGubu is a simple Python program that allows to create UI interfaces with Tkinter widgets.

So I have created an UI like this one here on the right

Now, I want that Scrollbar to be as big as the Text widget.

"How can I make the Scrollbar bigger on Tkinter" has been asked many times on StackOverflow. In my case, I cannot use the functions pack() or grid() as I am importing an already semi-finished UI

The code I use to load the Text and the Scrollbar is as the following:

    self.log = builder.get_object('log')
    self.log_scroll = builder.get_object('log_scroll')
    self.log.config(yscrollcommand=self.log_scroll.set)
    self.log_scroll.config(command=self.log.yview)

Now, I see two possibilities here:

1. Solving from PyGubu

The easiest way should be setting some attributes from PyGubu to solve this. Yet, PyGubu allows me to change only a minor number of attributes of the Scrollbar, and none of them seems to be relevant

2. Solving from Python

And here I have no idea about what to do. I don't know if I can use pack() and grid() while using a custom-made interface

Any help is appreciated